NOAA has released the numbers on July's temperatures within the US, and they continue the trend of what's been an exceptionally scorching year. With temperatures a full 3.3°F above the twentieth century average, it was the hottest month ever recorded within the US. While only one state (Virginia) set a record high monthly temperature, 32 different states across a broad sweep of the country had months that were in the top 10; combined, that made for an exceptional month.

But July is only the latest in a string of exceptionally hot months. The first seven months of this year were the hottest on record, and the 12-month period that includes it also set a record (narrowly beating out the 12 months that ended this past June). But simply describing records doesn't truly convey what an outlier this year is for the US; fortunately, NOAA has provided a graph that does so. As it clearly shows, every month since February is a serious outlier from historic conditions.

Enlarge/ How exceptional has 2012 been? The dark red trace shows how it's trending towards being the hottest calendar year on record by a significant margin.

Rainfall continued to be a problem, with up to 22 percent of the country reaching exceptional or extreme drought readings. The problem is exacerbated by the location of that 22 percent: the states that were the furthest below normal rainfall stretch east from Nebraska and Kansas to Illinois, which covers the US's agricultural heartland.

So far, the global figures for July haven't been released, so it's impossible to put these numbers in a broader context (the US occupies only about two percent of the Earth's surface). However, one of the major drivers of short-term climate variability, the El Niño-Southern Oscillation, has been shifting to a warm phase this year. This will probably push global temperatures even higher (since 2010, it's been in a cooler, La Niña mode).

Promoted Comments

For those of you noticing that there's something funny about the graph of each month's deviations from average - that they pretty much all decline from the beginning of year to the end of the year - there's an explanation. Notice that the graph is titled "Year-to-date Temperature Anomalies". As the year progresses, unusual temperatures in the first few days, weeks, and months are moderated by regression to the mean effects as more points are added later in the year. So, the leveling off is to be expected. It's just a slightly confusing presentation of those data.